The intracellular free Ca 2+ concentration of neurons in the CNS is highly regulated. Small changes in the cytosolic Ca 2+ concentration and different patterns of Ca 2+ transients are used to mediate important functional and developmental processes. In neurons both entry of extracellular Ca 2+ and release of Ca 2+ from intracellular stores are directly coupled to the activation of glutamate receptors and mediate physiological and pathophysiological processes. For the development of Alzheimer's Disease (AD) and age-related cognitive impairment, numerous reports indicate that both changes in the intracellular Ca2+ concentration promote pathogenesis. The present application will test the hypothesis that intracellular Ca 2+ channels (ICCs) contribute critically to physiological and pathophysiological functions of neurons affected with AD, age-related oxidative stress and age-related cognitive impairment. The localization, biophysical properties and physiological function of ICCs, of their isoforms and associated proteins in neurons of cell culture and animal models for AD and age-related cognitive impairment will be investigated. The main focus of the experiments will be on inositol 1, 4, 5-trisphosphate receptors, ryanodine receptors and a novel intracellular Ca 2+ channel, polycystin-2, which is expressed in neurons at high levels and has been characterized recently by others and us. Experiments for each type of ICC and its associated proteins will use a combination of light and electron microscope immuncytochemistry, single channel electrophysiology and optical imaging of intracellular Ca 2+ concentrations. The specific aims of this proposal are to determine changes in the subcellular localization of intracellular Ca 2+ channels; to analyze changed biophysical and pharmacological characteristics of intracellular Ca 2+ channels; and to measure the contribution of intracellular Ca 2+ channels to intracellular Ca 2+ signaling in AD and age-related cognitive impairment. Experiments will utilize neurons of both cell culture and animal models for Alzheimer's Disease and age-related cognitive impairment. Correlated data from immunolocalization, electrophysiology, and optical Ca 2+ imaging studies will allow the determination of mechanisms that influence intracellular Ca2+ concentrations in neurons and that may play a crucial role in the development of the pathophysiology of Alzheimer's Disease and age-related cognitive impairment. Thus, potential new targets for treating those devastating conditions affecting the aging population may be identified.